Novel polymers and dopes of aromatic polyamides containing a stilbene radical

ABSTRACT

NOVEL FILM- AND FIBER-FORMING AROMATIC POLYAMIDES AND COPOLYAMIDES CONSISTING ESSENTIALLY OF REPEATING UNITS OF THE FORMULA   -NH-R1-NH-CO-R2-CO-   WHEREIN R1 REPRESENTS A RADICAL SELECTED FROM THE GROUP OF 1,4 - PHENYLENE; METHYL - 1,4-PHENYLENE; CHLORO-1,4PHENYLENE; BROMO-1,4-PHENYLENE; FLUORO - 1,4-PHENYLENE; 4,4&#39;&#39;-BIPHENYLENE; 3,3&#39;&#39;-DIMETHYL-4,4&#39;&#39; - BIPHENYLENE; 3,3&#39;&#39;-DICHLORO-4,4&#39;&#39;-BIPHENYLENE; AND 1,4-, 1,5- AND 2,6-NAPHTHYLENE; AND R2 REPRESENTS THE 4,4&#39;&#39;-TRANS-STIBENYLENE RADICAL, WITH THE PROVISO THAT UP TO ABOUT 70 MOLE PERCENT, PREFERABLY UP TO ABOUT 50 MOLE PERCENT, OF THE 4,4&#39;&#39;- TRANSSTILBENYLENE RADICALS MAY BE REPLACED BY RIGID RADICALS SELECTED FROM THE GROUP OF 1,4-PHENYLENE, CHLORO-1,4PHENYLENE, AND 2,5-PYRIDYLENE. ANISOTROPIC DOPES MAY BE FORMED FROM SUCH POLYMERS.

United States Patent ice 3,801,528 NOVEL POLYMERS AND DOPES OF AROMATICPOLYAMIDES CONTAINING A STILBENE RADICAL Paul Winthrop Morgan, WestChester, Pa., assignor to 11;. du Pont de Nemours and Company,Wilmington,

e No Drawing. Filed Oct. 27, 1972, Ser. No. 301,288

' Int. Cl. C08g 51/44, 51/46', 51/50 U.S. Cl. 260-308 R 4 ClaimsABSTRACT OF THE DISCLOSURE Novel filmand fiber-forming aromaticpolyamides and copolyamides consisting essentially of repeating units ofthe formula H o o abmabtnrk wherein R represents a radical selected fromthe group of 1,4 phenylene; methyl 1,4-phenylene; chloro-l,4- phenylene;bromo-l,4-phenylene; fluoro 1,4-phenylene; 4,4-biphenylene;3,3'-di'methyl-4,4' biphenylene; 3,3'-dichloro-4,4' biphenylene; and1,4-, 1,5- and 2,6-naphthylene; and R represents the4,4'-trans-stilbenylene radical, with the proviso that up to about 70mole percent, preferably up to about 50 mole percent, of the 4,4'-transstilbenylene radicals may be replaced by rigid radicals selectedfrom the group of 1,4-phenylene, chloro-1,4- phenylene, and2,5-pyridylene. Anisotropic dopes may be formed from such polymers.

SPECIFICATION This invention relates to novel, filmand fiber-formingaromatic polyamides containing enchained 4,4-trans-sti1- benylene units,together with anisotropic spinning dopes.

BACKGROUND OF THE INVENTION The preparation of polyamides from (1)p,p'-stilbenedicarboxylic acid and diamines and from (2)4,4'-diaminostilbene and dicarboxylic acid halides is taught,respectively, in Toland U.S. Pat. 2,657,195 and in Adachi U.S. Pat.3,663,517. Anisotropic spinning dopes and high strength fibers ofaromatic polyamides are taught in Kwolek U.S. Pat. 3,671,542.

SUMMARY OF THE INVENTION This invention provides novel filmandfiber-forming aromatic polyamides and copolyamides consistingessentially of repeating units of the formula wherein R represents aradical selected from the group of 1,4 phenylene; methyl-l,4-phenyleue;chloro-1,4-phenylene; bromo-1,4-phenylene; fluoro-1,4-phenylene;4,4-biphenylene; 3,3'-dimethyl-4,4'-biphenylene; 3,3'dichloro-4,4'biphenylene; and 1,4-, 1,5- and 2,6-naphthylene; and Rrepresents the 4,4-trans-stilbenylene radical, with the proviso that upto about 70 mole percent, preferably up to about 50 mole percent, of the4,4-trans-stilbenylene radicals may be replaced by rigid radicalsselected from the group of 1,4-phenylene, chloro-l,4-phenylene, and2,5-pyridylene.

Useful Formula I polyamides and copolyamides exhibit inherent viscosityvalues of at least about 1.0, preferably 2.0 or higher, measured asdescribed hereinafter.

Preferably, Formula I polyamides and copolyamides are prepared by thereaction between diamines of the formula 3,801,528 Patented Apr. 2, 1974and diacid chlorides of the formula 11-13 oPp-m-fi-m wherein R and Rhave the significance set forth hereinbefore.

This invention also provides novel, optically anisotropic dopes whichare prepared from Formula I polyamides and copolyamides and concentratedsulfuric acid within the concentration range of about 98-104% H 50preferably about 99102%.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Useful polyamides andcopolyamides The polyamides and copolyamides of this invention may beprepared by low temperature solution polymerization processes similar tothose described in, e.g., Kwolek U.S. 3,063,966. In this process, acooled (e.g., with ice, ice-water, solid carbon dioxide) stirredsolution of a Formula II-A diamine, or mixture of diamines, is formed ina basic solvent system, e.g., a mixture of hexamethylphosphoramide(HMPA) and N methylpyrrolidone-2 (NMP). Other useful media are HMPAalone, N,N dimethylacetamide (DMAc), N,N,N',N' tetramethylurea (TMU),and mixtures thereof. 4,4'-trans-stilbenedicarbonyl chloride or mixturethereof with a suitable Formula II-B comonomer, e.g., terephthaloylchloride, is then added rapidly to the diamine solution. The diacidchlorides need not be mixed prior to their addition to the diaminesolution, but may be added separately. The reaction mixture may bestirred and/or allowed to stand until the desired degree ofpolymerization has been :achieved. Frequently, the reaction mixturebecomes a difficulty stirrable mass within a relatively short period oftime after addition of the acid chlorides. For some combinations ofintermediates the addition of anhydrous lithium chloride or calciumchloride to the amide medium, or the generation of such salts during ornear the end of the polymerization by addition of appropriate bases, isbeneficial in increasing the molecular weight of the product. It isconvenient to obtain the polymeric product by combining the reactionmixture, e.g., as a viscous solution or solid mass, with a polymernonsolvent, e.g., water, after which the polymer is collected byfiltration, washed (e.g., with water, acetone, alcohol), and dried priorto being dissolved to form the dopes of this invention. Duringpolymerization, the acidic hydrogen chloride by-prodnot generated by thecondensation reaction may be neutralized by adding to the reactionmixture a suitable neutralizing agent, e.g., lithium carbonate.

Formula II-A diamines useful for preparing the polyamides andcopolyamides and dopes of this invention include 1,4-phenylenediamine;ch1oro-, bromoand fluoro- 1,4-phenylenediamines; methyl 1,4phenylenediamine; benzidine, 3,3'-dimethylbenzidine;3,3'-dichlorobenzidine; and 1,4-, 1,5-, and 2,6-naphthalenediamines.Formula H-B diacid chlorides useful in this invention are 4,4-trans-stilbenedicarbonyl chloride and combinations thereof withterephthaloyl chloride, chloroterephthaloyl chloride, or2,5-pyridinedicarbonyl chloride.

Preferred Formula I polyamides are poly(chloro-1,4- phenylene4,4-trans-stilbenedicarboxamide) and poly- (1,4-phenylene4,4'-trans-stilbenedicarboxamide). Other useful polymers includepoly(4,4'-biphenylene 4,4'-transstilbenedicarboxamide),poly(3,3'-dimethyl-4,4-biphenylene 4,4-trans stilbenedicarboxamide),poly(methyl-1,4- phenylene 4,4-trans-stilbenedicarboxamide), and poly-(2,6-naphthylene 4,4-trans-stilbenedicarboxamide).

Additionally, up to a total of about 10 mole percent of the repeatingunits in the useful copolyamides of this invention may be derived fromreactants which do not conform to the Formulae II-A or II-B. Thesereactants, used in appropriate amounts, may be polyamide-formingaromatic monomers possessing both amine and acid chloride groups (e.g.,para-aminobenzoyl chloride hydrochloride); diamines and diacid chloridescharacterized by ring-atomring structures [e.g., bis(4-aminophenyl)etherand bis(4- chlorocarbonyl phenyl)ether]; and aliphatic diacid chloridescharacterized by 4-12 carbon atoms (e.g., adipyl chloride, sebacylchloride). When meta-oriented aromatic diamines and diacid chlorides(e.g., m-phenylenediamine and isophthaloyl chloride) are employed ascoreactants, preferably no more than about 5 mole percent of therepeating units are derived from these meta-oriented comonomers.

In preparation of the polyamides and copolyamides useful in thisinvention, chain terminators may be used. Among suitable chainterminators are compounds which can react monofunctionally with the acidchloride ends of these polymers, such as ammonia, ethylamine,dimethylamine, diethylamine, aniline, etc. Other terminators includehydroxylic compounds such as methyl alcohol, ethyl alcohol, isopropylalcohol, and phenol. Useful terminators which react monofunctionallywith the amine ends of these polymer chains include acid chlorides,e.g., acetyl chloride, acid anhydrides, e.g., acetic anhydride, andisocyanates, e.g., phenyl isocyanate.

Useful solvents The preferred solvent for preparing the anisotropicdopes of this invention is concentrated sulfuric acid within theconcentration range of about 98-104%, preferably 99l02%. Opticalanisotropy is described in detail in Kwolek US. 3,671,542.

Dope preparation The dopes of this invention are prepared by firstcombining under anhydrous conditions and with stirring and mixing,suitable quantities of the appropriate polymer or copolymer with thesulfuric acid to form compositions containing from about 620% by weightpolymer or c0- polymer, preferably about 1020% by weight. Generally,during addition of the polymer, the heat of mixing should be controlledin order that the temperature of the combined ingredients does notexceed 90 C., preferably not over 70 C. This may be accomplished byusing cooled quantities of acid, application of external cooling bathsto the mixing vessel, controlled rate of addition of the solid polymericmaterial, appropriate stirring action, and/ or combinations of theseprocedures. However, in some instances, as illustrated in the exampleswhich follow, it may be desirable to mix the ingredients with a moderatedegree of heating in order to achieve more rapid dissolution of thepolymeric solid. During preparation of the dope and the spinningthereof, the dopes should be maintained at temperatures which reduce theopportunity for polymer degradation to occur.

Since excessive water can interfere with the formation of dopes suitablefor spinning and can contribute to degradation of the polymer, dopesshould be prepared with relatively dry polymer samples under conditionswhere exposure to atmospheric moisture is minimized, e.g., under ablanket of dry nitrogen.

After being initially prepared, the dopes of this invention are veryviscous. Processing them into shaped articles, e.g., spinning fibers, isfacilitated by increasing their fluidity by means of adequate stirringor other shearing action.

One type of apparatus which is useful for increasing the fluidity ofthese dopes prior to spinning or casting is re err d to h rein as atwin-cell unit and is described below, together with fluid transfer andspinning equipment. This apparatus, into which the initially prepareddope is placed, consists of two open top cylinders (each of about 250ml. capacity) connected by a base block. Each cylinder has a hole in itsbase above a filter pack [3/50-mesh screens/U325 mesh screen/3/50 meshscreens (mesh/inch=mesh/2.54 cm.)] in the base block which leads to apassage in the block to the other filter pack and cylinder. The mixingdevice is fitted to a pair of pistons which closely fit each cylinder. Asmall hole in each piston is opened for the initial fitting by eachpiston to insure the removal of air and is then closed. A water bath,e.g., at about room temperature to about C., is placed around the mixingdevice. During the course of about 1 to 2 hours the dope is pushed bythe pistons from one cylinder to the other for several cycles, e.g.,8-15 cycles. With all of the dopes in one cylinder (and the connectingpassage), the mixing device is connected through a hole (previouslyplugged) in the base block leading to the connecting passage by a lengthof stainless steel tubing in the shape of a goose neck to anelectrically heated spinning block having a filter pack composed of/1/20-mesh screen/l/disc of Dynalloy filter material (X-5) (product ofFluid Dynamics Co., Morristown, NJ.) /2/ mesh-screens/ 1/325-meshscreen/2/ 100- mesh screens and an appropriately selected spinneret. Thewater bath is replaced around the mixing device and the tubing. Theshort length of the tubing between the water bath and the spinning blockwhich may be heated is insulated with glass wool. The dope is thenextruded from the spinneret, as shown in a following section.

Anisotropic character of the dopes The dopes of this invention areoptically anisotropic, i.e., microscopic regions of a given dope arebirefringent; a bulk dope sample depolarizes plane-polarized lightbecause the light transmission properties of the microscopic areas ofthe dope vary with direction. This characteristic is associated with theexistence of at least part of the dopes in the liquid crystalline ormesomorphic state. The liquid crystalline state of the dopes of thisinvention is of the nematic type.

The dopes of this invention which exhibit optical anisotropy do so whilethe dopes are in the relaxed state. This is in contrast to conventionalpolymer solutions which may be caused to depolarize plane-polarizedlight when subjected to appreciable shear.

There is a complex relationship existing among, e.g., the concentrationof the particular polymer or copoly-, mer species, the inherentviscosity thereof, the solvent system, and the dope temperature whichgenerally determines the ranges in which a given dope is anisotropic orisotropic. A useful polymer concentration-dope viscosity relationshipexists for given polymer-solvent combinations which are capable offorming the anisotropic dopes of this invention. For such combinations,the dope formed is isotropic when the polymer concentration is below aparticular level. As the concentration of the polymer is increased, theviscosity of the dope increases. However, at a point identified hereinas the critical concentration point there is a sharp discontinuity inthe slope of the viscosity v. concentration curve when the dope changesfrom isotropic to partially anisotropic without the formation of a solidphase. Further addition of polymer results in a decrease in theviscosity of the dope as it becomes more anisotropic. Illustrativeviscosity vs. concentration curves of this type are shown in Kwolek US.3,671,542. The critical concentration point (as well as the completeviscosity v. concentration curve) is routinely determined usingconventional concentration and viscosity measuring techniques (see US.Pat. 3,671,542).

Another qualitative determination of the anisotropic character of thesedopes may be made with the naked eye. These dopes may appear turbid orhazy and yet contain no, or practically no undissolved solid. When thedope, seen under reflected ordinary light, is disturbed by shaking orrolling the vessel containing the dope or by only slow stirring, thereis produced a characteristic, readily observed, satin-like sheen or glowwhich is observed even after the disturbance ceases, and which decreasesin intensity thereafter. This may be described as being a pearly oropalescent quality of the dope. Dopes which are disturbed as describedabove often give the appearance of having striations and/or graininessin the surface. These visual effects are observed in the anisotropicdopes of this invention. This may commonly be referred to as stiropalescence. Further details on qualitative and quantitivedeterminations of optical anisotropy are presented in Kwolek US. Pat.3,671,542. The latter patent describes the improved properties (e.g.,higher tenacity and initial modulus) of fibers spun from anisotropic,rather than isotropic systems.

Fiber preparation The dopes of this invention may be formed into fibersof high quality by spinning them into suitable baths.

The dopes of this invention may be spun into fibers by wet and air-gapspinning techniques, using spinnerets and other apparatus constructed ofmaterials resistant to the strong acids used. In air-gap spinning thespinneret is located in air or in an inert gaseous medium a shortdistance (e.g., 0.1 to cm., preferably from about 0.5 to 2 cm.) abovethe surface of a coagulat ing bath. Spinning of polyacrylonitrile fibersby one working of this general technique is described in, e.g., Ucci US.Pat. 3,080,210. A variety of baths may be used to coagulate the extrudeddope into fibers. The baths may be, e.g., water, as shown in theexamples, or a dilute solution of sulfuric acid. Preferably, thetemperature of a coagulation bath is room temperature or below.

It is desirable to completely remove the spinning solvent from fibersamples prepared from the dopes of this invention. Water alone oraqueous alkaline solutions may be used for removal of the residual acid.A convenient method is to spray the threadline as it leaves thecoagulating bath with an aqueous alkaline solution (e.g., saturatedsodium bicarbonate), remove the surface liquid from the threadline witha wiping device (e.g., a sponge) or a jet, wash with water to reduce theacid content, and wind up the fibers on bobbins. The fibers may besoaked in water for a period sufficient to remove the acid. Thethoroughly washed fibers may be dried on the bobbin in the area oftemperatures of up to about 110 C. They can also be conveniently driedon heated rolls.

It will be understood that theusual additives such as dyes, fillers,antioxidants, etc., can be incorporated into the dopes of this inventionfor the purpose intended, prior to shaped article preparation.

The fibers prepared from the acidic dopes of this invention exhibit highvalues of tensile properties, especially in the as-extruded state, i.e.,without subsequent hot drawing or annealing. The tensile properties ofthe fibers prepared from the dopes of this invention can be improved byhot drawing operations.

The as-extruded fibers of this invention, spun from the anisotropicdopes of Formula I polyamides and copolyamides, exhibit tenacity andinitial modulus values (measured as described hereinafter) of at least 3g.p.d. and 100 g.p.d., respectively, preferably of at least about 5g.p.d. and 200 g.p.d., respectively. These as-extruded fibers exhibitorientation angles of less than about 50.

The tensile properties of these as-extruded fibers can be enhanced bysubjecting the undrawn fibers to a heat treatment.

The excellent properties of the fibers of this invention areparticularly useful as reinforcing agents for plastic laminates, tirecords, V-belts, and the like.

6 MEASUREMENTS AND TESTS Inherent viscosity: Inherent viscosity (m isdefined by the following equation:

wherein (1 represents the relative viscosity and C represents aconcentration of 0.5 gram of the polymer in 100 ml. of solvent. Therelative viscosity (1 is determined by dividing the flow time in acapillary viscometer of a dilute solution of the polymer by the flowtime for the pure solvent. The dilute solutions used herein fordetermining (1 are of the concentration expressed by (C), above; flowtimes are determined at 30 C.; the solvent is sulfuric acid (96-98%)sulfuric). For some polymers, methane sulfuric acid may be the preferredsolvent.

Fiber tensile properties: Filament properties are measured on fibersthat have been conditioned at 21 C. and 65% relative humidity (R.-H.)for at least 16 hours unless otherwise specified. Yarn properties aremeasured on yarn that has been conditioned at 24 C. and 55% RH. for atleast 16 hours. All measurements are made in the fiber conditioningenvironment.

Tenacity (breaking tenacity) (T), elongation (breaking elongation) (E),and initial modulus (Mi) are obtained from breaking a single filament ora multifilament yarn on an Instron tester (Instron Engineering Corp.,Canton, Mass).

Single filaments are broken with a. gage length (distance between jaws)of 1.0 inch (2.54 cm.). The results on 3 filaments are averaged. Yarnsare given 3 turns per inch (2.54 cm.) twist (under 0.1 g.p.d. tension)and broken with a IO-inch (25.4 cm.) gage length. All samples areelongated at a constant rate of extension (10% elongation/minute forfibers having an E of under 8%, and 60% elongation/minute for fiberswith E of 8 to 100%) until the sample breaks.

The denier of a single filament (d.p.f.) is calculated from itsfunctional resonant frequency, determined by vibrating a 7 to 9 cm.length of fiber under tension with changing frequency. (A.S.T.M.Dl577-66, part 25, 1968). This filament is then used for 1 break.

The denier of yarn is determined by weighing a known length (at 0.1g.p.d. tension); cm. length is convenient.

The tenacity (grams/denier), elongation (percent), and initial modulus(gram/ denier) as defined in A.S.T.M. D2101, part 25, 1968 are obtainedfrom the load-elongation curve and the measured denier. In actualpractice, the measured denier of the sample, test conditions, and sampleidentification are fed to a computer before the start of a test; thecomputer records the load-elongation curve of the fiber as it is brokenand then calculates the fiber properties.

'It should be noted that different values are obtained from singlefilaments (filament properties) and from multifilament strands (yarnproperties) of the same sample. Unless specified otherwise allproperties given herein are filament properties.

Orientation angle: Orientation angle (O.A.) values for the fibers ofthis invention may be measured by the procedure described in Kwolek US.Pat. 3,671,542.

EXAMPLE 1 This example illustrates the preparation ofpoly(chloro-1,4-phenylene 4,4'-trans-stilbenedicarboxamide) and fibersthereof, spun from an optically anisotropic dope.

To a stirred solution of chloro-1,4-phenylenediamine (21.3 g., 0.15mole) in an ice-cooled mixture of HMPA/ NMP (350 ml./350 m1.) is added4,4'-transstilbenedicarbonyl chloride (45.75 g., 0.15 mole). The coolingbath is removed after 15 minutes and stirring of the clear, viscoussolution is continued. In another 15 minutes the reaction mixturebecomes diifcultly stirrable, whereupon it is permitted to standovernight at room temperature. The contents of the reaction vessel arecombined with water to precipitate the polymer which is collected,washed separately with water and with methanol, and dried in vacuo at 80C. The dried polymer exhibits an inherent viscosity of 2.11.

An anisotropic spinning dope containing 20% by weight solids is preparedby combining appropriate quantities of the polymer synthesized asdescribed above and concentrated sulfuric acid (99.58% H 50 The combinedingredients are transferred to the previously described twin-cell unitand are mixed thoroughly by being continually cycled at room temperaturefor a 2.5 hour period to form a spinnable dope.

The above-described dope, maintained at room temperature, is extrudedthrough a spinneret [20-hole, each hole of 0.002 inch (0.005 cm.)diameter, maintained at 50 C.] into an aqueous coagulating bathmaintained at C. and positioned inch vertically below the face of thespinneret. The fibers emerging from the bath are washed with water andwound up at the rate of 475 ft./ min. (145 m./min.). The washed anddried filaments exhibit the following tensile properties: T/E/Mi/Den.:6.2/ 3.84/369.5/2.34. The orientation angle is 33.

EXAMPLE 2 This example illustrates the perparation of coply(1,4-phenylene 4,4'-trans stilbenedicarboxamide/terephthalamide) (50/50) andfibers thereof which are spun from an optically anisotropic spinningdope.

To a stirred solution of 1,4-phenylenediamine (19.4 g., 0.18 mole) in anice-cooled mixture of HMPA/NMP (300 ml./300 ml.) is added4,4'-trans-stilbenedicarbonyl chloride (27.45 g., 0.09 mole) and, 30minutes later, terephthaloyl chloride (18.27 g., 0.09 mole). The coolingbath is removed and the reaction mixture is per-v mitted to warm to 60C. during the next 30 minutes. The temperature of the reaction mixtureremains at 60 C. for 1 hour (during which time it becomes difficultlystirrable); the reaction mixture is then permitted to stand overnight atroom temperature. The copolymer is precipitated, collected, washed, anddried by the procedure of Example 1. For the dried product, 1 -=3.O5.

An anisotropic spinning dope containing 20% by weight solids is preparedby combining appropriate quantities of the copolymer synthesized asdescribed above and concentrated sulfuric acid (99.58% H SO The combinedingredients are transferred to the previously described twin-cell unit,mixed thoroughly at 80 C. during the course of 30 minutes (9 cycles) toform an anisotropic spinning dope. This dope, maintained at 80 C., isextruded as described in Example 1 (but with the spinneret beingmaintained at 80 C.). The fibers emerging from bath are washed withwater and wound up at the rate of 500 ft./min. (152 m./min.). The washedand dried fibers exhibit the following tensile properties: T/E/Mi/Den.:4.8/2.3/380.1/2.3. The orientation angle is 29.

EXAMPLE 3 This example illustrates the preparation of copoly(chloro-1,4-phenylene, 4,4-trans stilbenedicarboxamide/terephthalamide)(95/5) and fibers thereof, spun from an optically anisotropic dope.

To a stirred solution of chloro-1,4-phenylenediamine (11.36 g. 0.08mole) in an ice-cooled mixture of HMPA/ NMP (350 ml./350 m1.) is added4,4'-trans-stilbenedicarbonyl chloride (23.28 g., 0.076 mole) and, 10minutes later, terephthaloyl chloride (0.81 g., 0.004 mole). The coolingbath is removed after an additional minutes and the reaction mixture ispermitted to warm to room temperature in the course of the next 45minutes, during which time it becomes difiicultly stirrable. Thecontents of the reaction vessel are permitted to stand overnight at roomtemperature, after which the copolymer is precipitated, collected,washed, and dried as described in Example 1. For the dried product=l.24.

An anisotropic spinning dope containing 20% by weight solids is preparedby combining appropriate quantities of the copolymer synthesized asdescribed above and concentrated sulfuric acid (100.03% H SO Thecombined ingredients are transferred to the previously describedtwin-cell unit, mixed thoroughly at room temperature during the courseof 30 minutes (9 cycles) to form an anisotropic dope. This dope,maintained at room temperature, is extruded as described in Example 1,except that the spinneret is maintained at 70 C. The fibers emergingfrom the bath are washed with water and are wound up at the rate of 490ft./min. (1 49 m./min.). The washed and dried filaments exhibit thefollowing tensile properties: T/E/Mi/Den.: 7.1/4.7/ 362.7/ 3.3. Theorientation angle is 29.

EXAMPLE 4 This example illustrates the preparation of copoly-(chloro-1,4-phenylene 4,4'-trans stilbenedicarboxamide/2,5-pyridinedicarboxamide) (95/5) and fibers thereof, spun from anoptically anisotropic dope.

To a stirred solution of chloro-1,4-phenylenediamine (11.36 g., 0.08mole) in an ice-cooled mixture of HMPA/ NMP (350 ml./ 350 ml.) is added4,4'-trans-stilbenedicarbonyl chloride (23.28 g., 0.076 mole) and, 10minutes later, 2,5-pyridinedicarbonyl chloride (0. 82 g., 0.004 mole).The cooling bath is removed after an additional 5 minutes and thereaction mixture is permitted to warm to room temperature during thenext 45 minutes. The reaction mixture, now an unstirrable gel, ispermitted to stand at room temperature for an additional hour. Thecopolymer is precipitated, collected, washed, and dried by the procedureof Example 1. For the dried product, =2.35.

An anisotropic spinning dope containing 20% by weight solids is preparedby combining appropriate quantities of the copolymer synthesized asdescribed above and concentrated sulfuric acid (100.03% H SO Thecombined ingredients are transferred to the previously describedtwincell unit, mixed thoroughly at C. during the course of 30 minutes (9cycles) to form an optically anisotropic dope. This dope is extruded asdescribed in Example 1, except that the spinneret temperature ismaintained at 50 C. The fibers emerging from the bath are washed withwater and wound up at the rate of 545 ft./min. (166 m./min.). The washedand dried filaments exhibit the following tensile properties:T/E/Mi/Den.: 8.1/ 4.0/ 423.3/ 1.9. The orientation angle is 28".

EXAMPLE 5 This example illustrates the preparation of copoly-(l,4-phenylene 4,4 trans stilbenedicarboxamide/terephthalamide) (30/70)and fibers thereof, spun from an optically anisotropic dope.

To a stirred solution of 1,4-phenylenediamine 19.44 g., 0.18 mole) in anice-cooled mixture of HMPA/NMP (300 ml./300 ml.) is added4,4'-trans-stilbenedicarbonyl chloride (16.38 g., 0.054 mole) and, 10minutes later, terephthaloyl chloride (25.56 g., 0.126 mole). Thecooling bath is removed after an additional 5 minutes and the reactionmixture is permitted to warm to 60 C. during the next 45 minutes. Thereaction mixture, now difiicultyly stirrable, is permitted to stand atroom temperature overnight. The copolymer is precipitated, collected,washed, and dried by the procedure of Example 1. For the dried product,m =2.9l.

An anisotropic spinning dope containing 20% by weight solids is preparedby combining appropriate quantities of the copolymer synthesized asdescribed above and concentrated sulfuric acid (99.58% H 80 The combinedingredients are transferred to the previously described twincell units,mixed thoroughly at 60 C. during the course of 30 minutes (9 cycles) toform an anisotropic dope. The

dope, maintained at 75 C., is extruded as described in Example 1, exceptthat the spinneret is maintained at 75 C. The fibers emerging from thebath are washed with water and wound up at the rate of 570 ft./min. (174m./min.). The washed and dried filaments exhibit the following tensileproperties: T/E/Mi/Den.: 8.3/3.2/473.6/2.4'. The orientation angle is 23EXAMPLE 6 This example illustrates the preparation of poly(1,4-phenylene 4,4'-trans-stilbenedicarboxamide) and an optically anisotropicdope thereof.

To a stirred solution of 1,4-phenylenediamine (5.4 g., 0.005 mole) in anice-cooled mixture of HMPA/NMP (300 ml./ 300 ml.) is added4,4-trans-stilbenedicarbonyl chloride (15.25 g., 0.005 mole). Thecooling bath is removed after 15 minutes and the reaction mixture ispermitted to warm to room temperature over the next 45 minutes. Afterthe reaction mixture is permitted to stand for an additional hour atroom temperature, it is combined with water to precipitate the polymerwhich is collected, washed, and dried by the procedure of Example 1. Forthe dried product, 1 =l.37.

A dope containing 12% by weight of this polyamide in 100.03% sulfuricacid is optically anisotropic at room temperature.

What is claimed is:

1. Polymer consisting essentially of repeating units of the formulawherein R represents a radical selected from the group of 1,4-phenylene;methyl-1,4-phenylene; chloro-1,4-phenylene; bromo-1,4-phenylene;fluoro-1,4phenylene; 4,4'-biphenylene; 3,3-dimethyl-4,4-biphenylene;3,3-dichloro-4, 4'-biphenylene; and 1,4- 1,5- and 2,6-naphthylene; and Rrepresents the 4,4'-trans-stilbeneylene radical, with the proviso thatup to about mole percent, preferably up to about 50 mole percent, of the4,4'-trans-stilbeneylene radicals may be replaced by rigid radicalsselected from the group of 1,4-phenylene, chloro-1,4-phenylene, and 2,5-pyridylene, said oplymer having an inherent viscosity of at least 1.0 asmeasured at a concentration of 0.5 gram of polymer in 100 ml. ofsulfuric acid (96-98% sulfuric) at 30 C.

2. The polymer of claim 1 wherein R is 1,4'-phenylene.

3. The polymer of claim 1 wherein R is 4,4'-transstilbeneylene.

4. An anisotropic dope consisting essentially of from 10 to 20% of thepolymer of claim 1 in concentrated sulfuric acid (98-104% sulfuric).

References Cited UNITED STATES PATENTS 2,997,391 4/1957 Murry 260-857 RX 2,657,195 10/ 1953 Toland 260- 3,67!1,542 6/1972 Kwolek 260-308 R3,663,517 5/1972 Adachi 260-78 R 3,289,970 8/1966 Epstein 260-3083,555,071 l/1971 Rao 260-453 MORRIS LIEBMAN, Primary Examiner R.ZAITLEN, Assistant Examiner US. Cl. X.R. 260-78 R

